Mean monthly temperatures for June were 2 to 5 degrees F warmer than normal, the 9th consecutive month with warmer than normal conditions going back to last September (2011). In fact the first half of this year has been warmer than any year since 1987. Extremes for the month ranged from 98 degrees F at New Ulm (June 27) to 30 degrees F at Embarrass (June 1st). Some observers reported 7 days with high temperatures of 90 degrees F or higher, and the National Weather Service had to issue Heat Advisories (Heat Index up to 105 degrees F) for a some areas. On a few days and nights dewpoints climbed into the 70s F, making for uncomfortable sleeping. Minnesota did not report the lowest temperature in the nation on any days during the month of June.

Rainfall for June was generally above normal for most observers (the 3rd consecutive month for some), except for those in northwestern and southwestern counties, most of which reported below normal rainfall. For some June total rainfall was record-setting, including Cannon Falls (15.11"), Wright (13.03"), Island Lake (11.06"), Red Wing Dam (10.95"), Moose Lake (10.42"), Duluth (10.03"), and Two Harbors (9.49"). The two most notable events of the month were the flash floods on June 14-15 in southeastern counties (Cannon Falls 8.83") and on June 19-20 in northeastern counties (7-10 inches in the Duluth area). Many observers reported measurable rainfall on 13-15 days during the month.

Winds in June were far diminished compared with April and May, and closer to normal. There were a few reports of exceptionally strong wind gusts over 70 mph on June 17th (near Appleton), and over 80 mph on June 19th(Scott County). The associated thunderstorms on these dates brought large hail as well. A weak tornado touched down near Belle Plaine on June 10th. June was the 4th consecutive month (Mar, Apr, May, Jun) with at least one tornado report filed in the state.

Topic: New Record Low Annual Heating Degree Days for the Twin Cities

The Minnesota State Climatology Office noted this week as the annual Heating Degree Day (HDD) season (July 1 to June 30) comes to an end, that 2011-2012 brought a new record low number for HDD with only 5852. The previous record low value was 6611 recorded in 2005-2006. HDD are calculated using the mean daily temperature when it falls below a base of 65 degrees F. Thus on a day with a mean daily temperature value (maximum + minimum/2) of 50 F, the HDD value would be 15. These are accumulated daily as an index for energy use to heat homes and commercial buildings.

Topic: Weekly Weather potpourri

Tropical Storm Debby spun off the coast of the Florida panhandle bringing record amounts of rainfall to some areas this week. Tallahassee reported 8.80 inches from the storm, while Apalachicola reported nearly 13 inches. Further east and south Gainesville reported nearly 14 inches, while Tampa reported nearly 10 inches. Some cooperative observers reported over 20 inches, and many streets were flooded. Several tornadoes were reported associated with Tropical Storm Debby as well.

Elsewhere thunderstorm rains were bringing some relief and help to fire fighters in Colorado, where wildfires have been burning this week. Earlier in the week temperatures in the upper 90s F to over 100 degrees F had combined with single digit relative humidity readings and moderate winds had allowed many wildfires to spread rapidly. Hundreds of homes have been destroyed by these fires.

Tropical Storm Doksuri was spinning southeast of Hong Kong in the Western Pacific Ocean with winds up to 70 mph and sea waves over 20 feet. It was expected to bring heavy rainfall to areas south of Hong Kong over the weekend, before dissipating.

In science news, it was reported this week that scientists from Cardiff, Denmark, Sweden, and Russia have discovered a 3 billion year old impact crater in West Greenland. The is the oldest known impact crater on Earth from among 180 other known sites. This one was probably caused by an asteroid or comet. You can read more about it at...

NASA and NOAA announced this week the deployment of new sensors aboard the Suomi NPP polar-orbiting satellite are already assisting forecasting with numerical weather prediction. This represents a record speed for deployment of satellite data following launch, because it has only been seven months since the satellite went into orbit. Usually, there is a longer test and calibration period before the data are utilized. You can read more about this new satellite system at...

MPR listener question: It is coming up on the anniversary of the famous BWCA "blow down" on July 4, 1999, called a "derecho" storm. What type of storm is this and how frequent are they?

Answer: Yes, indeed, arguably the most destructive storm of this type, the derecho of July 4, 1999 brought a 600 square mile swath of straight line winds, 80-100 mph, across the BWCA leveling 250,000 acres of timber valued at $12-$18 million. This storm was highly organized as it traveled 1300 miles from eastern North Dakota to the New England states.

Derecho is a Spanish term meaning "direct" or "straight ahead." It was used back in 1888 by Dr. Gustavus Hinrichs of the University of Iowa to describe the strong winds that accompanied severe thunderstorms and to distinguish them from the rotating winds of a tornado. Derechos usually arise from a mesoscale convective complex composed of an organized cluster of interacting thunderstorms. They typically show up as a bow echo on Doppler radar systems. Fortunately these storms are rare, averaging 10-12 per year across the USA, and only appearing in Minnesota about every 5-6 years, mostly in the months of June, July, or August.

Twin Cities Almanac for June 29th:

The average MSP high temperature for this date is 81 degrees F (plus or minus 8 degrees F standard deviation), while the average low is 61 degrees F (plus or minus 7 degrees F standard deviation).

Average dew point for June 29th is 58 degrees F, with a maximum of 77 degrees F in 19963 and a minimum of 38 degrees F in 1988.

All-time state records for June 29th:

The state record high temperature for this date is 110 degrees F at Canby (Yellow Medicine County) in 1931. The state record low temperature for this date is 27 degrees F at Pine River Dam (Crow Wing County) in 1925. State record precipitation for this date is 6.37 inches at Worthington (Nobles County) in 1969; and no snowfall has been reported on this date.

Past Weather Features:

June 29-30, 1877 brought some heavy thunderstorms to parts of Minnesota, with 3.48 inches at St Paul. Elsewhere Fort Ripley saw 1.70 inches and Duluth reported 1.50 inches. In fact it was a wet June in Duluth with over 5 inches of rainfall, and measurable rainfall on 16 days.

June 24-30, 1931 brought the worst June Heat Wave in Minnesota history. Over two dozen Minnesota communities reported daytime highs of 100 degrees F or greater. Overnight lows at Canby never fell below 87 degrees F on the 28th and 29th. Crops wilted in the heat. July 1st brought some relief as temperatures dropped back into the 70s and 80s F.

In the drought year of 1988 June 29 brought frost to northern Minnesota. Brimson was 29 degrees F and Gunflint Lake dropped to 30 degrees F. Cotton, Isabella, Tower and Mora also reported frosts.

Outlook:

Warmer than normal temperatures continuing into the weekend and next week. Chances for scattered and isolated showers and thunderstorms each day, particularly on Tuesday. General dominance of high pressure next week will keep most places dry.

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